Renal Function Testing and Urinalysis - Gustafson

Question 1

Urea

Answer 1

BUN - blood urea nitrogen
Normal 8-25 mg/dl
Body’s way of disposing of ammonia
Urea filtered by glomerulus

Question 2

When blood flow is low, what happened to urea?

Answer 2

Tends to be reabsorbed passively. Rises faster than creatinine when the kidney is underperfused

Question 3

3 Types of azotemia

Answer 3

Prerenal - kidney is underperfused - 20/1
Renal - the kidney is damaged - < 10
Postrenal

Question 4

What can cause an increased BUN?

Answer 4

Increased protein catabolism
Diet high in protein
Upper GI bleed
Physiological stress

Question 5

Potential causes of pre renal azotemia

Answer 5

Dehydration
Hemorrhage/shock
Congestive heart failure
Liver failure - hepatorenal syndrome

Question 6

What can cause renal azotemia

Answer 6

Acute renal injury
Medications
Acute kidney disease
Chronic kidney disease

Question 7

What can cause post-renal azotemia

Answer 7

Urine is blocked

• prostatism
• stone
• injury
• stone

Question 8

What can cause decreased BUN?

Answer 8

Protein malabsorption
Protein wasting - nephrotic syndrome
Liver failure
Overhydration

Question 9

Creatinine

Answer 9

Breakdown of creatine phosphate, released from skeletal m
Normal 0.6-1.3 gm/dL (up to 2.0 in body builder)
Filtered by glomerulus and secreted by the tubules

Question 10

Increased creatinine

Answer 10

A sensitive marker for kidney failure
Huge muscle mass
Medications
Cooked meat
Rhabdomyolysis
Does NOT require 24 hour collection

Question 11

What is the classic estimate of glomerular filtration rate?

Answer 11

Creatinine clearance

Normal - 90-120 mL/min

Question 12

What GRF lab result is associated with chronic kidney disease?

Answer 12

Below 90 mL/min

Question 13

Cystatin C

Answer 13

Gamma trace protein

Produced by all nucleated cells and is superior to creatinine

Question 14

What is the urine sodium concentration in pre renal azotemia/shock/hepatorenal syndrome?

Answer 14

< 20 mEq/L

Question 15

What is urine sodium concentration in acute renal injury?

Answer 15

> 40 mEq/L

Question 16

FENa calculation

Answer 16

Urine Na x Serum Cr / Serum Na x Urine Cr

Question 17

FENa values for pre renal azotemia and acute renal injury

Answer 17

DUBE was a huge fan of this
Prerenal azotemia - < 1%
Acute renal injury > 2%

Question 18

What are 3 ways to estimate specific gravity?

Answer 18

Hydrometer (urineometer)
Refractometer
Dipstick

Question 19

How do you measure the osmolality of urine in the lab?

Answer 19

Using an osmometer

Question 20

Lab values in acute renal injury

Answer 20

SG - 1.010

Osmolality close to plasma - 300 mOsm/Kg

Question 21

Lab values in pre renal azotemia

Answer 21

SG high

Osmolality > 500 mOsm/Kg

Question 22

Polyuria

Answer 22

Urine > 3 L/day

If osmolality > 300mOsm pt has a solute diuresis (probably glucose or ketone)

Question 23

What effect can bacteria have on a urine specimen?

Answer 23

Zero glucose
Alkaline urine
Vanished formed elements

Question 24

What does cloudy urine mean?

Answer 24

Lots of white cells due to infection
OR
Harmless crystals that are forming as it cools

Question 25

Red urine can be caused by what 4 things?

Answer 25

Blood
Myoglobin
Porphyria
Beets

Question 26

What does yellow fluorescence in urine indicate?

Answer 26

Heavily loaded with riboflavin (Vit B)

Question 27

What does a foamy head on a urine sample indicate?

Answer 27

Usually proteinuria or conjugated bilirubinuria

Question 28

What is the SG for dilute urine and what can it indicate?

Answer 28

< 1.007
Diabetes insipidus
Or pt drank shit ton o’ water

Question 29

Isosthenuria

Answer 29

SG stuck at 1.010

Suggests renal tubules are not working

Question 30

pH

Answer 30

Important for crystal analysis

Question 31

If you are acutely sick, how much protein is it normal to have in your urine?

Answer 31

Trace

Question 32

Ketones

Answer 32

Low levels - missed a meal
High - diabetic ketoacidosis
L-Dopa can cause a positive test

Question 33

Asymptomatic hematuria is indicative of what?

Answer 33

Kidney or bladder cancer until proven otherwise

Question 34

Possible causes of myoglobinuria?

Answer 34

Muscle injury, overexertion or rhabdomyolysis

Question 35

Nitrite

Answer 35

A metabolite of bacterial metabolism

Question 36

What type of bilirubin will make it into the urine?

Answer 36

Conjugated

The unconjugated form isn’t water soluble

Question 37

Elevated urobilinogen indicates?

Answer 37

Either too much bilirubin being put out (your hemolyzing) The urobilinogen from color is sneaking past liver

Question 38

What pad on the dipstick is useful for picking up bacterial UTIs?

Answer 38

The Leukocyte alkaline esterase

-each spot is a neutrophil

Question 39

RBCs come from where?

Answer 39

Glomerular bleeding

Question 40

What makes glitter cells in the urine?

Answer 40

White cells - brownian movement

Question 41

What can indicate that a urine sample has been contaminated?

Answer 41

Vaginal squamous cells
Pollen
Candida

Question 42

Tamm-Horsfall protein

Answer 42

A glycoprotein made by the tubules

A few hyaline casts made of this are normal

Question 43

Epithelial cell casts indicate what disease?

Answer 43

Acute tubular necrosis

Question 44

What are common causes of oxalate crystals?

Answer 44

Stones
Vit C
Antifreeze
Spinach
Crohns

Question 45

What indicates that you have a urea splitter infection?

Answer 45

Magnesium ammoniam phosphate crystals

Question 46

Leucine bicycle wheels indicate?

Answer 46

Liver failure